/Engine/Plugins/Developer/Concert/ConcertSync/ConcertSyncClient/Source/ConcertSyncClient/Public/IConcertClientWorkspace.h
the delegate called every time an activity is added to or updated in the session.
[FOnActivityAddedOrUpdated](API\Plugins\ConcertSyncClient\FOnActivityAddedOrUpdated) & OnActivityAddedOrUpdated()